In 1996, they moved in together. In 2001, they tied the knot, with Leyva's blessing. "He is not my biological son, but I am his father," Alvarez says. "The only difference is blood. Everything else, we are very similar in every way."

Alvarez and Gonzalez's coaching prowess, meanwhile, grew as their partnership strengthened. Hundreds of kids passed through their gym, including a litany of recent champions: Ari Barrera, who won the national championship on the still rings in 2001, when he was 12; Rocky Kaller, who captured a 2003 Florida Gymnastics Championship when he was 11; and Jorge Giraldo, who won a gold medal for Colombia at the 2012 Pacific Rim Championships. Jessica Gil Ortiz, a former student of Gonzalez's, will represent her native Colombia in this summer's Olympics.

But one prodigy — a formerly asthmatic kid who just happened to be Gonzalez's son — would be their greatest project of all.

Giulio Sciorio

Leyva has always been hard on himself. "I hate messing up."

Giulio Sciorio

Yin Alvarez (left) encourages his stepson and best student before a big routine.

It's shortly after 11 a.m. on June 19 inside Universal Gymnastics. The training center is packed with kids in a summer camp program. The musky scent of sweat fills the space. While Gonzalez teaches a small group of girls the proper way to spin on the uneven bars, Alvarez watches his stepson stretch for a practice run on the vault.

Dressed in a white T-shirt and shorts, Leyva ignores Alvarez's gaze. The 20-year-old stands five feet seven inches and has freakishly long arms and large hands. He also has a bigger frame and a bulkier build than most of the men in his sport.

Running full speed, Leyva catapults himself into the air. He does a double-twist, double-flip before landing on a pile of foam squares. Alvarez points out a minor mistake when Leyva's hands hit the vault. "You are not coming down straight when you land," the coach scolds. "You need to concentrate harder."

Leyva rolls his eyes and sulks away. "I know, Yin," he hisses.

Alvarez shoots back, "Well, if you know, let's get it right."

It's been ten days since Leyva lost the 2012 men's national title by .05 percentage points to John Orozco, all because of little mistakes just like the one Alvarez caught. Without grueling daily practice, gymnasts lose their flexibility, rhythm, and sense of space. The slightest error means the difference between first and second place in a competition. With an Olympic berth on the line, Leyva can't afford to slip up even a centimeter.

The journey that took Leyva to this level of precision began when he was just 3 years old, while watching a gymnastics video at Alvarez's house. "I pointed at the TV and said, 'That's what I want to do,'" Leyva recollects.

His mother had no intention of turning him on to gymnastics. She didn't think his health or his body would allow him to excel. With proper medication in Miami, his asthma was finally under control, but she fretted that the chalk used in the sport would trigger his allergies. Leyva was also flat-footed and clumsy, and his long arms put him at a disadvantage for the pure strength required on the still rings.

"A gymnast has to be strong, coordinated, and have the right type of physique," Gonzalez says. "I thought it would be too difficult for him."

Alvarez also tried to make Leyva forget about gymnastics. "Yin would take me to the park to play baseball," Leyva says. "But I would get bored."

Finally, Alvarez persuaded Gonzalez to let him train the boy when he turned 4. At first, Leyva was awful. "I was very, very bad," he says. "I'll never forget at my first competition, when I was 5, I got a last-place medal. That moment shaped me. I realized what I had to do to get where I wanted to be."

Gonzalez was soon amazed by her son's unrelenting spirit. "When he was a kid, he would endlessly watch video of great gymnasts on the parallel bars so he could learn from them," she says. "He would even mimic the techniques with his action figures."

By the time Leyva was in the first grade, he was committed to the sport full-time. His parents pulled him out of public school, but he was far from alone — Alvarez and Gonzalez also offered homeschooling to roughly 25 boys and girls who were training to compete for state and national championships. The group included their top gymnasts, Barrera, Kaller, and Ortiz.

Leyva's days had a steady routine: training from 9 a.m. to 4 p.m., followed by late afternoons and early evenings with a tutor. Wednesdays were off for field trips. "We'd take the kids to the beach or to the movies," Gonzalez says. "The kids also got an hour and a half for lunch. But instead of going out, they usually stayed at the gym."

Like his parents and their comrades at the Cuban gymnastics school, Leyva and his peers at Universal Gymnastics have formed close friendships. His best friends are Barrera and his brother Alex, who both started at Universal in 1995. Last year, when one of Leyva's dogs bit him in the face while his parents were out of town, the first person he called was Alex. "It is a friendship that is going to last their entire lives," Gonzalez says.

danell you make me proud to be my cousin. I remember you when you were a small child when your paraents and grandparents used to visit my parents house. I see that you also inherited your great grandmother my (Tia Hilda) aunt the love for the piano and music. I wish you the best in everythingyou do.